Conventionally, use of polyurethane resin having photoelasticity as a sensor such as a pressure-sensitive sensor has been proposed.
For example, Patent Document 1 below has proposed a touch panel including a polyurethane molded article for a pressure-sensitive sensor made of polyurethane resin, and a light generating unit and a light receiving unit that are provided so as to sandwich the polyurethane molded article for a pressure-sensitive sensor (see below).
The touch panel detects birefringence caused inside the polyurethane molded article for a pressure-sensitive sensor when a pressure is applied by, for example, a finger based on attenuation of light that was allowed to exit from the light generating unit and enters the light receiving unit.